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A small moss turns professional

Over the last few years, the small moss Physcomitrella patens has been used extremely successfully in international research laboratories and has become an important model organism, alongside fruit flies (Drosophila) and thale cress (Arabidopsis). However, there is one small issue preventing it from becoming a true “professional”: No standards are available on the proper storage and documentation of sample material, areas in which every research group does what suits it best. However, in February 2010, the “International Moss Stock Centre” (IMSC) was established at the University of Freiburg and is rapidly changing this situation. Researchers led by Prof. Dr. Ralf Reski have developed a method that enables them to store biological material in a cryobank for an indefinite period of time and thaw it when needed. International Physcomitrella patens research now has a long awaited central resource centre at its disposal.

Research needs to be reproducible: an experiment carried out by a particular research group with a genetically modified organism must be documented in order to enable the experiment to be repeated by any other research group. "This means that a growing number of scientific journals require mutants and ecotypes to be given a reference number," said Prof. Dr. Ralf Reski, head of the Department of Plant Biotechnology at the University of Freiburg. "The ideal scenario is to store back-up samples of biological samples in a biobank and provide access to the samples to whoever requires them," said Reski who focuses on Physcomitrella patens research. P. patens is an inconspicuous moss that over the last few years has become an important model organism for molecular biology and genetic research. Prior to the establishment of IMSC, research groups used to store their samples in their own fridges. If another group of researchers decided to repeat a published experiment, they had to contact the original researchers and hope that the samples had not already died or been destroyed. The establishment of the "International Moss Stock Centre" (IMSC), which was co-financed by the Freiburg Centre for Biological Signalling Studies (BIOSS), provides the international Physcomitrella community with a central resource centre that does away with this problem.

Unlimited cold storage?

"We published the Physcomitrella genome in 2008. Since then, an ever increasing number of research groups are focusing on the plant," said Reski. Ingrid Heger, who is in charge of storing the samples in tanks kept in the basement of the Institute of Biology II, is also aware of the growing interest in the plant. "We are being contacted by increasing numbers of PhD students and even diploma students," said the biologist. "It is becoming more and more obvious that people around the world are seeking to find out about methods associated with Physcomitrella research." The central storage centre now takes work on the moss to a "professional" level. However, a centre of this kind can only be established when procedures are available that enable the long-term storage of plant material. Ten years ago, Reski developed such a method in cooperation with BASF AG in a project focusing on the collection of thousands of genetic Physcomitrella patens mutants. The know-how gained at that time is now being put to good use by the international moss community. "I was convinced we would not have received public funding; that is why we sought industrial cooperation partners," said Reski.

Since the establishment of the centre in February 2010, Ingrid Heger has been receiving up to two calls per week from people interested in Physcomitrella samples and that number is growing. Some researchers are interested in a mutant listed on the centre's homepage; and others are interested in depositing their own mutants in the centre's cryotanks. In the case of the latter, Ingrid Heger is sent the particular sample which she then chaffs and transfers into a specific medium that protects the cells against the long-term consequences of freezing. The vial is then placed into a liquid nitrogen container. The liquid nitrogen gas phase can reach temperatures as low as -196°C. The samples are stored slightly above the gas phase at -160 °C. All vital processes are arrested and can be restored ten, a hundred or even a thousand years later. It is possible to very quickly transform a frozen cell back into a plant. 100% of the biological material survives the procedure due to a special chemical treatment. Previously, scientists stored their moss samples at 4°C, and the plants usually died within a few months.

Green biobank

“The newly established central infrastructure will considerably improve the exchange of information and samples between researchers around the world,” said Reski. “In addition, researchers planning to use Physcomitrella patens in addition to other model organisms will find it easier to gain access to Physcomitrella patens research.“

Reski and his fellow researchers provide their services to basic researchers as well as to biotechnology companies. Since the secrecy of their work, especially in the initial phases, is crucial to such companies, IMSC store the material “under public exclusion”, i.e. other interested parties have no right of access to the samples. “Our resource centre is just like any other biobank,” said Reski going on to add “in future, we might also offer the possibility to deposit other moss species, like endangered species for example.” As the samples stored in the freezers are each barely bigger than a fingernail, there is room for hundreds of thousands of samples in the containers in the basement of the Freiburg-based institute.